1. Field of the Invention
This invention relates to devices for determining distances to objects. More particularly, the invention relates to a range finder which measures distance by comparing a known curvilinear form or spectrum of points with the object being measured.
2. Prior Art
Various devices are known in the prior art for determining distances to objects, including devices which rely on stadia principles. In these devices, a series of marks representing different distances are compared against an image of the object being viewed and the distance of the object from the viewer can thus be determined. However, specific major portions of the object must be visible in their entirety in order to obtain a measurement.
Examples of some such prior art devices are disclosed in the following U.S. Pat. Nos.: 3,749,494, 3,859,732, 3,977,086, 4,016,654, 4,263,719 and 4,367,949. None of these patents disclose a device in which several different size out-lines or spectrum of points of an object are provided, against which the actual object being viewed is compared to determine the distance of the object from the viewer, and particularly where only a portion of the object being viewed need be visible in order to make an accurate measurement.
Other prior art devices rely upon electronic image sensing. In these devices, an object to be sensed electronically is generally focused by a lens onto a photodiode array where the image is effectively changed from light energy to electrical energy. A photodiode array generally has two unique information sets for each diode. The first information set determines the location of the diode. The second information set determines the intensity of the reflected light from the object.
The information of the first set is presented in a distinct manner representing a position immediately before and immediately after the subsequent and preceeding locations, respectively. This information might typically be designated as location X,Y. For example, if a point is referred to as location 100,11, this point will be located physically on an array containing 10,000 points at a position at the extreme right hand side of the array and 11 rows down from the top. In other words, digitized information is available which can be processed in a computer.
The information of the second set is presented in an analog manner and indicates the light intensity. This light intensity can be seen on an oscilloscope as y=mx, where black .ltoreq.y.ltoreq. white and m is the slope of the line. In other words, a straight line or linear relationship exists between the diode signal x and the corresponding contrast y.